Tuesday, February 7, is Missouri's Presidential Preference Primary. Polls will be open from 6 AM to 7 PM. Sample ballots for each party can be found on the St. Louis City Board of Elections web site.
You can also check out their website to verify your current polling place. In addition to the previously discussed change from Marian to Mann School as a 15th Ward polling place, many people changed wards last fall. So be sure to check your voter card or the website for your current polling place.
Anyone who wants to participate as a delegate in the Democratic convention (or participate in the selection process of ward delegates in March) must have voted in this Primary. (Update: This rule has been dropped for 2012.)